The actuator assembly is widely used to position a transducer head which reads and writes data to selected tracks in a hard disc drive. A pivot cartridge supports the actuator assembly to provide smooth rotational movement of the assembly to pivot the transducer between tracks. The actuator assembly includes an actuator body having a bore into which the pivot cartridge is attached. The pivot cartridge can be attached to the bore by threaded fasteners, set screw, retaining ring, press-fit or adhesives.
One important mechanical resonance in the rotational movement of the actuator assembly is the pivot bearing translational mode. The servo bandwidth for high track density application where a higher frequency is required is limited by the frequency of this translational mode. For a given actuator assembly, this mode is determined by the pivot stiffness and the attachment method of the pivot cartridge to the actuator body.
For using threaded fasteners, set screw or press-fit, the pivot cartridge is forced to contact one side of the bore of the actuator body. Examples of such attachment methods suitable for use in disc drives, can be found in the specification of U.S. Pat. No. 5,146,450 entitled “Method and Apparatus for Bearing to Comb Attachment”, by Peter E. Brooks et al, granted Sep. 8, 1992, U.S. Pat. No. 5,654,849 entitled “Molded Swing-Type Actuator Assembly With Press-Fit Pivot and Spring-Loaded Ground Conductor Elements”, by Payman Hassibi et al, granted Aug. 5, 1997 and U.S. Pat. No. 6,018,441 entitled “Disk Drive Pivot Bearing and Actuator Arm Assembly”, by Ruyue Y. Wu et al, granted Jan. 25, 2000. Although these attachment methods will give a higher translational mode frequency, they are however costly and time-consuming to assemble.
For using retaining ring, the cost is lower and easily assembled and disassembled. But, in comparison to the other methods, the retaining ring method suffers from lower translational mode frequency. At average, the frequency drops to approximately 5˜10%. Unlike the more complicated methods, there is no contact between the pivot cartridge and the bore of the actuator body. Likewise, using adhesives will also result in lower translational mode frequency.
There remains a need for an improved and cheaper method to increase the frequency of the translational mode of the actuator assembly so that a higher servo bandwidth can be reached. It will be evident from the following description that the present invention offers this and other advantages.